Sheet slowdown mechanism



June 24, 1969 J. STMNES 3,451,670

I SHEET SLOWDOWN MECHANISM I Filed Nov. 0. 1967 Sheet I of 5 INVENTOR.

' ALFRED (ISTA/N'J June 24 1969 A. J. STAINES 3,451,670

SHEET SLOWUOWN MECHANISM ofS Sheet 2 INVENTOR. ALFRED J STA/N58 June 24,1969 A. J. STAINES 3,451,670-

I SHEET SLOWDOWN MECHANISM Filed Nov. 6, 1967 Sheet 3 of 3 I 4 I 7 ixNvEATToR. FIG 4 All-RED J sun/-55 United States Patent 01 ice 3,451,670Patented June 24, 1969 3,451,670 SHEET SLOWDOWN MECHANISM Alfred J.Staines, Shaker Heights, Ohio, assignor to Harris- IntertypeCorporation, Cleveland, Ohio, a corporation of Delaware Filed Nov. 6,1967, Ser. No. 680,860

Int. Cl. B65h 29/68 US. Cl. 271-68 Claims ABSTRACT OF THE DISCLOSURE Asheet slow-down mechanism which includes a rotatable driven vacuum wheeloperable to applya braking force to flexible moving sheets to reduce thespeed of the sheets is provided. An adaptor unit operable to reduce thespeed of rigid, relatively heavy sheets straddles the vacuum wheel andis rotatable relative to the drive shaft of the vacuum wheel betweeninoperative and operative positions. A sheet blow-down means moves thesheets downwardly relative to the vacuum wheel and adaptor unit and theexhaust of a vacuum pump for applying a suction to the vacuum wheel andadaptor unit is directed to the blow-down means to provide the airblast. l

sheet. Such a slow-down mechanism is shown in United States Patent No.2,657,052. While such mechanisms have operated satisfactorily inreducing the rate of speed of flexible sheets which bend and readilyconform to contour of the wheel, they have not been satisfactory forreducing the'rate of speed of relatively heavyshee tjs, commonly andhereinafter referred to as. boards, ,since the boards will not readilyconform to the peripheral contour of the vacuum wheel and .have arelatively high inertia due to the weight thereof and thus'require arelatively greater braking force to be applied thereto to effect slowingthereof.

To reduce the rate of speed of moving boards, suction members separatefrom the vacuum wheel and which are adapted to be attachedand detachedfrom the slow-down support structure have been provided. These suctionmembers usually have a planar board engaging surface surrounding avacuum port and a suction in the port draws the board against the boardengaging surface as it is moved thereover. These suction members,,however, have not been very satisfactory in operation. Because of thehigh inertia of a moving board, a high vacuum braking force must beapplied to the boards to slow them when the equipment with which theslow-down mechanism is associated is conveying the boards at a normalspeed. However, when the conveying speed of the boards is reduced, theinertia thereof is likewise reduced and the vacuum braking forcesometimes is so great that it causes the slower moving board to cling toor hang-up on the suction member. The clinging board blocks the vacuumfrom acting on the subsequently conveyed boards. Thus, no or littlevacuum braking is applied to the subsequently conveyed boards and due tothis failure, the board may become crumpled causing a disarrangement ofthe pile even when the clinging board is removed. Various techniques foralleviating these problems, such as varying the vacuum pressure, theport size and the area of the board engaging surface, have not beenentirely satisfactory.

Accordingly, an important object of the present inven-' tion is theprovision of a new and improved sheet slowdown mechanism which overcomesthe above-noted problems, is of a highly practical and economicalconstruction, and is selectively operable to reduce the rate of speed ofeither flexible relatively light sheets or rigid relatively heavyboards.

Another object of the present invention is the provision of a new andimproved sheet slow-down mechanism for reducing the rate of speed ofmoving rigid relatively heavy boards and which includes a suction meanslocated adjacent the path of board travel for drawing the moving boardsthereagainst to apply a braking force thereto and a cooperablyassociated rotatable wheel engageable with the boards to move the samerelative to the suction means when the latter clings or hangs up on thesuction means to efiect removal therefrom.

A further object of the present invention is the provision of a new andimproved sheet slow-down mech anism which is selectively operable toreduce the rate ofspeed of either flexible relatively light sheets orrigid relatively heavy sheets after the sheets are released by movinggrippers and which includes a rotatable vacuum wheel operable to slowthe relatively flexible sheets and an adaptor means for slowing therelatively rigid heavy sheets and which adaptor means is supported formovement between an inoperative position at which the adaptor means islocated when flexible sheets are being conveyed and an operativeposition at which the adaptor means is located when the rigid sheets arebeing conveyed. A still further object of the present invention is theprovision of a new and improved sheet slow-down mechanism having an airblast blow-down for moving a sheet downwardly relative to a suctionslow-down member and wherein the air blast blow-down is automaticallycontrolled by the position of the sheet relative to the slow-downmechanism. Another object of the present invention is the provision of anew and improved sheet slow-down mechanism, as noted in the nextpreceding paragraph, wherein a vacuum pump has its exhaust outletconnected to the blowdown mechanism and airis directed through theexhaust outlet and to the blow-down mechanism when the vacuum pump drawsair through the suction slow-down member so that the blow-down timing iscontrolled by a sheet covering and uncovering a suction port of thesuction member. Q

Yet another object of the present invention is to provide a new andimproved sheet slow-down mechanism for reducing the rate of speed ofmoving flexiblesheets upon being released by grippers moving through apath at a given speed, and which includes a vacuum wheel for grippingthe sheets upon being released by the grippers and which is rotatable ata surface speed less than the speed of the moving sheets and an airblow-down means for directing an air blast against the sheets to movethe latter downwardly against the vacuum wheel, and wherein the vacuumwheel and air blow-down means are of a construction and arrangement suchthat they effect only a slight drag on the sheets while they are beinggripped by the grippers and moved thereover prior to being releasedwhereby marking of the underside of the sheets and/or smudging of theprinted material thereon, if the sheet is printed, is prevented orsubstantially minimized- The invention further resides in certain novelconstructions and arrangements of parts, and further objects andadvantages thereof will appear from the following detailed descriptionof the preferred embodiment described with reference to the accompanyingdrawings, which form a part of the specification, and in which likereference characters designate corresponding patrs throughout theseveral views and wherein:

FIG. 1 is a fragmentary side elevational view of a sheet deliveryapparatus embodying the slow-down mechanism of the present invention;

FIG. 2 is a fragmentary sectional view of the apparatus of FIG. 1 takenapproximately along line 22 of FIG. 1;

FIG. 3 is an enlarged view of part of the apparatus shown in FIG. 2 andlooking in the direction of the arrows 3-3 of FIG. 2;

FIG. 4 is an enlarged sectional view taken approximately along line 4--4of FIG. 2;

FIG. 5 is a sectional view on a larger scale taken approximately alongline 5-5 of FIG. 4;

FIG. 6 is a sectional view like that shown in FIG. 4 but showing certainparts thereof in a different position;

FIGS. 7-9 are fragmentary sectional views of part of the slow-downmechanism of the present invention and showing a board moving thereoverin different positions relative thereto;

FIGS. 10-12 are fragmentary sectional views of part of the slow-downmechanism of the present invention and showing a flexible sheet movingthereover in different positions relative thereto; and

FIG. 13 is a schematic view illustrating the vacuum circuit for theslow-down mechanism of the present invention.

The present invention provides a novel sheet slowdown mechanism forreducing the rate of speed of a moving sheet. Although the novel sheetslow-down mechanism of the present invention could be used in or withvarious kinds of apparatus in which it is desired to reduce the rate ofspeed of a moving sheet, it is especially adapted for use in a sheetdelivery apparatus wherein moving sheets are to be slowed down prior tobeing deposited onto a pile, and for the purposes of illustration, isshown in the drawings as being embodied in a sheet delivery apparatus 10for a printing press.

The sheet delivery apparatus '10 is adapted to deliver printed sheetsfrom a printing press (not shown) to a delivery pile 12. The sheetdelivery apparatus 10 includes an endless chain conveyor 14 supported bya pair of spaced side frames 15, 16 for conveying the printed sheetsfrom the printing press to a position above the pile 12. The conveyor 14is operated in timed relationship with the printing press so that theleading edges of the sheets are gripped by moving grippers 20 mounted ongripper bars 22 extending transversely of the conveyor 14. The conveyor14 conveys the sheets from the printing press along its lower run 23until the grippers 20 engage a stationary cam 24 which functions to openthe grippers 20 to release the sheets being conveyed thereby. Thegripper bars 22 are spaced apart a distance somewhat greater than themaximum length of the sheet which the sheet delivery apparatus 10 isdesigned to handle.

Beneath the lower run 23 of the conveyor 14 there is a pile supportplatform 25 upon which the sheets drop by gravity upon being released bythe grippers 20. The sheets upon being released by the grippers 20' aredeflected downwardly toward the pile 12 by fingers 27. The sheets areguided or aligned at the front edge of the pile 12 by pile guides 28secured to a rod 29 extending transversely between the side frames and16.

When the sheets are dropped onto the pile 12 they are jogged intocorrect lateral alignment by suitable side jogger plates, omitted fromthe drawings for the sake of simplicity. The sheets are also joggedendwise to place them in endwise alignment by a jogger means 40 which isreciprocably movable through forward and return strokes in a directionparallel to or substantially parallel to the direction of the sheettravel.

The jogger means 40 comprises a plurality of jogger plates 41 located atspace transverse locations between the side frames 15, 16 of thedelivery apparatus 10. The jogger plates 41 have vertically disposed,planar sheet engaging surfaces 42 and are mounted on a horizontallydisposed support shaft 43 extending transversely of the side frames 15,16 and having its opposite ends secured to support brackets 44, 45 (seeFIG. 2). The support brackets 44, 45 are respectively supported adjacenttheir upper ends on horizontally disposed support slides or members 46,47, the support slides 46, 47 in turn being slidably supported by spacedbrackets 49 respectively fixed to the side frames 15, 16 of the deliveryapparatus 10. The support brackets 44, 45 are adapted to be clamped tothe support slides 46, 47 by thumb screws 50, 51 in threaded engagementwith side plates 52, 53 having their upper and lower ends secured to thebrackets 44, 45 respectively.

The jogger plates 41 are adapted to be reciprocated through theirforward and return strokes toward and from the pile guides 28 by anactuating means 54 operatively connected with the rearward or left endsof the support slides 46, 47, as viewed in FIG. 1., The actuating meanscomprises a pair of levers 55 having one end pivotally connected to theadjacent rearward end of the support slides 46, 47 and the other endfixed to a shaft 56. The shaft 56 is rotatably supported in the sideframes 15, 16 and is adapted to be rotated in opposite directions tocause the levers 55 to be oscillated to and fro by a suitable drivemeans (not shown) operatively connected with the shaft 56.

From the foregoing, it should be apparent that when the levers 55 areoscillated to and fro, the support slides 46, 47 are reciprocated to andfro in a direction of sheet travel. Movement of the support slides 46,47 to and fro causes the support brackets 44, 45 and the jogger plates41 to be reciprocated toward and from the front pile guides 28. Theactuating means 54 is actuated in timed relationship with the deliveryapparatus 10 so that the jogger plates 41 are reciprocated through theirforward and return strokes for each sheet handled by the conveyor means14 and preferably so that the jogger plates 41 are at the end of theirforward stroke or at the beginning of their return stroke when thegrippers 20 release the sheets. The jogger plates 41 engage the droppedsheets during their forward stroke to move them into endwise alignmentwith the pile 12.

The jogger means 40 is adjustably positionable longitudinally of thesupport slides 46, 47 so that different size sheets can be jogged intoendwise alignment. To this end, the support slides 46, 47 on theirunderside are each provided with gear teeth to form a rack 60. The racks60 are each in meshed engagement with a pinion gear 61 rotatablysupported by the adjacent brackets 44, 45. Each of the pinion gears 61,in turn is in meshed engagement with the drive gear 62 fixed to a shaft63 having its opposite ends rotatably supported by the brackets 44, 45.

The jogger means 40 is adjusted longitudinally of the support slides bybacking off the thumb screws 50, 51 to unclamp the brackets 44, 45 fromthe support slides 46, 47 and then rotating a handwheel 64 fixed to oneend of the shaft 63. Rotation of the handwheel effects rotation of theshaft 63 and the gears 62 and 61, which in turn causes the brackets 44,45 and the jogger plates 41 carried thereby to be moved longitudinallyrelative to the support slides 46, 47.

In accordance with the provisions of the present invention, a novelsheet slow-down mechanism 70 is provided for reducing the rate of speedof the moving sheets prior to their being deposited onto the pile 12.The slow-down mechanism 70 is carried by the support brackets 44, 45 andis selectively operable to reduce the rate of speed of both highlyflexible relatively light sheets, such as paper, and relatively rigidheavy sheets or boards. The sheet slow-down mechanism 70 is oper- 5 Vable to grip the trailing end of each sheet at the time its forward endis being released by the grippers 20 and to slow down or reduce the rateof speed of the moving sheet so that the sheet is gently deposited onthe pile 12. The sheet slow-down mechanism 70 is effective to preventthe moving sheets from crashing into the front pile guides 28 at a highvelocity due to the forward momentum or inertia they possess upon beingreleased by the grippers 20 and thus, prevents the forward edge of thesheets from crumpling and/or being damaged.

The sheet slow-down mechanism 70 comprises a plurality of slow-downdevices 72 disposed beneath the lower run of the conveyor 14 and locatedat spaced transverse locations between the side frames 15, 16 of thedelivery apparatus 10. -Each of the slow-down devices 72, in theillustrated embodiment, is an assembled unit which is clamped on ahorizontally disposed support shaft 74 having its opposite ends fixed toand supported by the support brackets 44, 45. Since each of theslow-down devices 72 is of an identical construction, only the leftmostslow-down device 72, as shown in FIG. 2, will be described in detail.

The slow-down device 72, in general, comprises a nonrotatable vacuumshoe member 75 having a vacuum port 76 located adjacent the path ofsheet travel and a rotatable vacuum wheel 77 having a plurality ofperipherally spaced slots 78 open to the atmosphere and which aresuccessively placed in communication with the vacuum port 76 in responseto rotation of the wheel 77 to create a suction at the periphery of thewheel 77. The vacuum wheel 77 is partially disposed adjacent the path ofsheet travel and is operable to grip flexible sheets to reduce theirrate of speed and then'release the same for deposit onto the pile 12.The slow-down device 72 further comprises a suction'or adaptor means 80movable relative'to the vacuum shoe member 75 between an inoperativeposition remote from the path of sheet travel and an operative positionfor effecting a reduction in the rate of speed of moving boards. Whenthe adaptor means 80 is in its operative position, the boards are brakedthere by to reduce their rate of speed. i

The vacuum shoe member 75 has a projecting or hub portion 82 extendingparallel to the shaft 74 and a depending leg 83 at one end of theprojecting portion 82. The depending leg 83 at its'end remote from theprojecting portion 82 is in the form of a split clamp 'and is adapted tobe clamped to the shaft 74', as by suitable screws 84. The projectingportion 82 has opposed outer peripheral surface portions 85, 86 whichare cylindrical and concentric with respect to the axis of rotation 87of the vacuum wheel 77. The. vacuum port 76 extends generally radiallyinwardly from the peripheral surface 85 and communicates with an axialpassageway 88 in the vacuum shoe 75; The passageway 88 in turn isconnected with a vacuum pump 89 (shown schematically 1n FIG. 13) toapply a vacuum at the port 76. As best shown in FIGS. 4 and 6, thevacuum port 76 is disposed forwardly or to the right of a vertical planepassing through the axis 87 of rotation of the vacuum wheel 77 nadincludes .a main port portion 90. and a recess portion 91-.

The main port portion 90 is of a constant diameter and its side wallextends parallel 'to a line passing through the center of thepassageway88 and the axis of the shaft 87. The recess portion 91.extends along the periphery of the surface 85 in a direction oppositethe direction of sheet travel and is of a substantially lesser depththan the main port portion 90.

slots 78 are outwardly divergent, radial through slots whichsuccessively communicate with the vacuum port 76 upon rotation of thevacuum wheel 77.

The vacuum wheel 77 is rotated relative to the stationary member 75 inthe direction of sheet travel, or in a clockwise direction, as shown inFIGS. 4 and 6, by a drive means operatively connected with an integrallyformed sleeve portion 101 at the other end of the vacuum wheel 77. Thedrive means comprises a drive shaft 102 which is rotatably journalled inthe vacuum shoe member 75 by bushings 103. The drive shaft 102 isrotatably supported at its opposite ends by the support brackets 44, 45.The drive shaft 102 is drivingly connected with a sleeve portion 101 ofthe vacuum wheel by a drive collar 104 in driving engagement with thesleeve 101 and which is removably secured to the shaft 102 by a setscrew 105.

The drive shaft 102 at one end is fixed to a bevel gear 106 which is inconstant mesh with a bevel gear 107 rotatably journalled on a sleeve 108carried by the support bracket 44. The sleeve 108 is drivingly connectedwith a shaft 109 having its opposite ends rotatably supported by theside frames 15 via a splined connection. The splined connection betweenthe sleeve 108 and shaft 109'permits the support bracket 44, 45 to beadjustably positioned longitudinally relative to the support arms 46, 47while maintaining a driving connection with the shaft 109. The shaft 109is drivingly connected with a conventional or suitable variable speedtransmission 110 by a chain and sprocket drive 111, the variable speedtrans mission 110 in turn being drivingly connected to an electric motor112 via a V-belt drive 113.

The vacuum wheel 77 is rotated by the drive means so as to have aperipheral or surface speed which is substantially less than the speedof the moving sheets being conveyed by the conveyor 14. Although thesurface speed of the vacuum wheel 77 can be varied by suitably adjustingthe variable speed transmission 110, the surface speed of the vacuumwheel 77 is preferably set to the weight and speed of the stock, butwith the maximum set speed being approximately /5 of the maximum speedof the conveyor 14.

As previously mentioned, the slow-down device 72 also includes a suctionor adaptor means cooperably associated with the vacuum wheel 77 forreducing the rate of speed of moving boards. The adaptor means 80straddles the vacuum wheel 77 and has its sheet engaging surface 81disposed substantially tangentially of the periphery of the vacuum wheel77. The adaptor means 80 comprises a pair of generally annular sidemembers 1 10, 111 disposed on the opposite sides of the vacuum wheel 77and a cross member 112 located radially outwardly of the periphery ofthe vacuum wheel 77. The Side and cross members are bolted together bybolts116 to form a unitary structure. The side members 110, 111 havefiat peripheral surface portions and define with the cross member 112 aU-shaped planar sheet engaging surface 81. The side members and 111 aremade from a suitable wear resistant antifriction material so as toenable the vacuum wheel to freely rotate relative to the adaptor means80.

The sides 110, 111 and the cross member 112 define a vacuum chamberlocated between the sheet engaging surface 81 and the periphery of thevacuum wheel 77. The vacuum chamber 115 is open to the atmosphereandcommunicates with the slots 78 in the vacuum wheel 77. The vacuumchamber 115 includes a main chamber portion in communication with theperiphery of the vacuum wheel 77 and a recessed portion 117 surroundingthe first portion and which is of a lesser depth than the first portion.The recess portion has a tapered bottom surface 1-18 which convergestoward the main portion proceeding from the sheet engaging surface 81toward the main portion of the vacuum chamber 115. The provision of thetapered recess portion enables the boards as they are drawn against theadaptor means 80 to mofe or less conform to the contour of the bottomsurface 118 to prevent air from leaking between the board and the sheetengaging surface 81 to the vacuum chamber 115.

The adaptor means 80 is movable between operative and inoperativepositions shown in FIGS. 4, 6, respectively. When in its operativeposition, the sheet engaging surface 81 extends substantially parallelto the direction of sheet travel and it operates to reduce the rate ofspeed of moving boards. When in its inoperative position, the sheetengaging surface 81 is remote from the path of sheet travel so that onlythe vacuum wheel 77 is disposed within the path of sheet travel. Theadaptor means 80 is moved to its inoperative position when it is desiredto reduce the rate of speed of very flexible sheets. To this end, theside member 111 is rotatably journaled on the sleeve portion 101 of thevacuum wheel 77 by a bushing 121 and the side 110 is slidably disposedon the outer peripheral surfaces 85, 86 of the projecting portion 82 ofthe stationary member 75.

The adaptor means 80 is adapted to be locked or retained in both itsoperative and inoperative positions when moved thereto to preventrelative rotation between '5 the adaptor means 80 and the stationarymember 75. To this end, the side member 110 is provided with a pair bfspaced flats 123, 124 as peripherally spaced locations and the leg 83carries a stop member or key 125 having a fiat surface 126 which isadapted to engage either the fiat 123 or 124 to prevent rotation of theadaptor means 80 relative to the stationary member 75. The key 125 ismounted on the depending leg 83 of the stationary member 75 by a pair ofscrews 127.

When it is desired to move the adaptor means 80 relative to thestationary member 75 between its operative and inoperative positions,the set screw 105 of the drive collar 104 is backed off and the drivecollar i104, vacuum wheel 77 and adaptor means 80 are moved axially ofthe shaft 102 toward the right, as viewed in FIG. 5, until therespective fiat 123 or 124 of the side member 110 is disengaged from thefiat 126 on the key 125. The adaptor means 80 is then rotated to itsother position and moved along with the vacuum wheel 77 axially of theshaft 102 toward the left until the other flat on the side member 110thereof engages the fiat 126 on the key 125. Then the collar 104 ismoved axially of the shaft toward the left until it engages thecooperating key on the drive sleeve portion 101 and the set screw 105 istightened. From the foregoing, it should be apparent that the adaptormeans 80 can be readily and easily moved between its operative andinoperative positions and that it is of a relatively simple andeconomical construction.

When it is desired to reduce the rate of speed of moving boards beingconveyed by the conveyor 14 of the delivery apparatus 10, the adaptormeans 80 is moved to its operative position, as shown in FIG. 5, inwhich position the sheet engaging surface 81 thereof is disposedparallel to the path of sheet travel. The vacuum wheel 77 is thenrotated and the vacuum pump 89 started to create a vacuum in-the vacuumchamber 115 of the adaptor means 80. As the moving board is being heldby the grippers and being conveyed over the slowdown device 72, thevacuum created in the vacuum chamber 115 will draw the board against thesheet engaging surface 81. When the grippers 20 release the front edgeofthe boards, the vacuum force in the vacuum chamber 115 will draw theboard into tight engagement with the sheet engaging surface 81 (see FIG.8) and grip or apply a braking force to the board to reduce the rate ofspeed of the same. The boards upon being drawn into tight engagementwith the sheet engaging surface '81 continues to move forwardly towardthe pile 12.

If a board clings or hangs up on the surface 81, as discussed above, thevacuum wheel effects movement off of the sheet engaging surface 81 andonto the pile. Specifically, the vacuum wheel 77 engages the trailingend of the board and effects movement of the same forwardly relative tothe adaptor means 80 while the vacuum force is being fully appliedthereto to maintain the sheet in engagement with the adaptor means 80.As the vacuum wheel 77 moves the board relative to the adaptor means 80,the trailing edge of the board will begin to uncover the recess portion91 of the port 76 whereupon air will leak or flow from the atmospheretoward the port (see FIG. 9).

The advantages of the present construction are that the problems ofboard hang-up experienced with prior art devices are completely overcomeor minimized. These problems are overcome by the provision of the vacuumwheel 77, which effects movement of the board forwardly relative to theadaptor means 80* in the event of a board hanging up.

It should be noted that the entire slow-down mechanism '70 is alsoreciprocated to and fro in a direction parallel to the direction ofsheet travel along with the jogger means 40, since it is also supportedby the support brackets 44, 45. The reciprocating movement of theslow-down mechanism 70 and the jogger means 40 is preferably timed withrespect to the operation of the delivery apparatus such that the joggermeans 40 'and slow-down mechanism 70 are either at the end of theirforward stroke or are beginning their return stroke when the grippers 20release the sheets or boards. Since the slow-down mechanism 70 is movingthrough its return stroke when the boards are tightly drawn against theadaptor means "80, an additional slow-down effect is achieved, since theslow-down mechanism 70 is moving in a direction opposite to thedirection of the momentum of the boards upon being released. The boarddeposited onto the pile 12 is jogged into endwise alignment by thejogger plates 41 during the next forward stroke of the jogger means 40.

When it is desired to reduce the rate of speed of very flexible sheets,the adaptor means 80 is moved from its operative position to itsinoperative position, shown in FIG. 6. When in this position the movingiflexible sheets will be drawn into engagement with only the vacuumwheel 77. FIG. 10 shows the relative position of a flexible sheetwith-respect to the slow-down device 72 while it is held by the grippers20 and being moved thereover by the conveyor 14. Due to the dispositionof the vacuum port 76, a slight flow of air, as indicated by the arrow130, from the atmosphere between the flexible sheet and the wheel 77toward the port 76 takes place. Due to this slight air flow, only apartial vacuum force is exerted on the flexiblesheet'so that aslightdrag on the sheet is effected to placethe sheet under aslight'tension while it is being held .by the grippers 20. By exertingonly a slight drag on the sheet, marking of the sheeton its underside-and/or smudging of theink, if the underside is printed, is prevented orsubstantially minimized.

When the grippers 20 releases the flexible sheet, the sheet will bedrawn into tight engagement with the periphery of the vacuum wheel, asshownin FIG. 11, and no air flow from the atmosphere to the port 76 willoccur. The rate of speed of the moving (flexible sheet upon beingreleased by the grippers 20 will be reduced bythe vacuum wheel 77. Asthe sheet is being moved forwardly toward'the pile 12 by the wheel 77,its trailing edge begins to uncover the recessportion 91 of the vacuumport 76whereupon a slight air flow through the slots 78 in the wheel 77to the port 76 takes place. As the wheel 77 continues to rotate thetrailing edge progressively uncovers more of the port-76 toprogressively decrease the vacuum force acting on the sheet until thetrailing edge of the sheet is disposed in a radial plane passingthrough. the approximate center of the port-whereupon the 'vacuum forcewill. no longer be sufficient to hold the sheet'on the wheel 77 andthus, the sheet will be released and move forwardly onto the pile 12.

A vacuum is created in each of the vacuum ports 76 of'the stationarymembers 75 of each of theslow-down devices 72 by the vacuum pump 89. Thevacuum pump 89 has its inlet connected by a conduit 131 to a distributormanifold 135 having a plurality of outlets, one for each.

of the slow-down devices 72, which are connected-by flexible hoses 136to the respective passageway 88 in the stationary members 75 of thedevices 72.

The slow-down mechanism 70 also includes a blowdown or air blast means140 disposed above the slowdown devices 72 for directing air underpressure against the upper side of the sheets to force the sheetsdownwardly into engagement with the sheet engaging surface 81 of theadaptor means 80 or the vacuum wheel 77 and to defleet the sheetsdownwardly onto the pile 12 upon being released by the slow-down devices72. The blow-down means comprises a pair of spaced conduits or pipes141, 142 extending transversely of the side frames 15, 16, the conduits141, 142 being located rearwardly and forwardly of the slow-down devices72, respectively. The pipes 141:, 142 are connected at their oppositeends to supports 144, 145 respectively bolted or otherwise secured tothe upper end of the brackets 44, 45. The pipes 1-41, 142 are providedwith a plurality of longitudinally spaced nozzlelike openings 148 ontheir bottom side through which air supplied thereto under pressure isdirected downwardly and transversely of the direction of movement of thesheets. The pipes 141, 142 are preferably in communication with oneanother by suitable cross pipes 149.

Another feature of the present invention is that operation of the airblast means 140 is intermittent and automatically controlled so as tooccur prior to the sheets being gripped by the slow-down devices 72 andafter the trailing edge of the sheets uncovers the ports 76. To thisend, the pipe 141 is connected via a flexible hose 150 to the exhaust oroutlet of the vacuum pump 89. Thus, air is directed from the nozzle-likeopenings 148 of the pipes 141, 142 only when the vacuum port 76 in thestationary member 75 is in communication with the atmosphere.

From the foregoing, it can be seen that an air blast is directed fromthe nozzle-like openings 148 transversely of the direction of sheettravel while the sheet is being moved over the slow-down device 72 bythe grippers 20 on the conveyor 14 to force the sheet into engagementwith the wheel 77. This is due to the fact that as long as the grippers20 are holding the sheets (see FIG. a slight leakage of air from theatmosphere to the port 76 takes place. However, when the grippersrelease the sheet and it is drawn into tight engagement with the wheel77, the port 76 no longer communicates with the atmosphere and thus, noair blast occurs since no air is exhausted by the vacuum pump 89. An airblast is again established against the sheet and against the next sheetbeing conveyed by the conveyor 14 upon the trailing edge of the sheetbeing moved by the vacuum wheel to a position such that it partiallyuncovers the recessed portion 91 of the vacuum port 76. This insuresthat just prior to the time that the sheet is released from the vacuumwheel 77 or adaptor means 80, an air blast is directed thereagainst tomove the same downwardly toward the pile 12 in addition to thegravitational force acting thereon.

The advantages of connecting the blow-down means 140 to the exhaust ofthe vacuum pump 89 are that no separate compressed air source isrequired, that the intermittent air blast will always be properly timedfor each sheet. Moreover, no adjustable timing valves are required whichwould require adjusting upon adjustment of the slow-down mechanism.

The pressure of the air blasts can be readily controlled by providing asuitable release valve in the exhaust line between the vacuum pump andinlets 147 which automatically opens when the pressure of the air isabove a predetermined pressure.

It should also be noted that since the slow-down devices 72 comprise anassembled unit and are clamped to the shaft 74, they can be adjustedtransversely between the side frames relative to eachother and the sideframes by merely loosening the screws 84 and repositioning the unitsrelative to the shaft 64. Additionally it can be seen that by supportingthe blow-down means from the brackets 44, 45, which also support theslow-down devices 72 and the jogger plates 40, 41 that the blow-downmeans will always be properly positioned relative to the devices 72.

From the foregoing, it should be apparent to the hereinbefore enumeratedobjects and others have been accomplished and that a novel sheetslow-down mechanism for use in reducing the speed of moving boardsand/or to reducing the speed of both flexible sheets and moving boardshas been provided. While the illustrated embodiment of the presentinvention has been described in considerable detail, it is hereby myintention to cover all con: structions, modifications and arrangementscoming within the ability of those skilled in the art and within thescope and spirit of the present invention.

Having described my invention, I claim:

1. In a mechanism which is selectively operable'to reduce the speed of amoving substantially rigid relatively heavy sheet or a moving flexiblerelatively light sheet after the sheet is released from moving gripperswhich move the sheet through a path, sheet slow-down means including avacuum wheel mounted adjacent the sheet path and having vacuumpassageways opening to the atmosphere adjacent said path, means forrotating said vacuum wheel in the direction of sheet movement and at aspeed less than the speed at which a sheet is moved by the grippers,means for applying a vacuum to said passageways to secure a flexiblesheet around a circumferential portion of said vacuum wheel therebyeffecting a slowing of the flexible sheet, means for slowing a rigidsheet including a rigid sheet slow-down adapter means having a sheetengaging surface, means supporting said adapter means in first andsecond positions and for movement between said positions, said adaptermeans when in said first position being remote from said path andpositioned thereat when flexible sheets are being conveyed and saidadapter means when in said second position being adjacent said sheetpath and positioned thereat when rigid sheets are being conveyed, thesheet engaging surface of said adapter means defining a vacuum chamberlocated radially outwardly of said vacuum wheel and having an area opento the atmosphere adjacent said sheet path when said adapter means is insaid second position, and said vacuum chamber having an opening incommunication with said vacuum passageways in said vacuum wheel tothereby have a vacuum applied thereto to effect drawing of a rigid sheetagainst the sheet engaging surface of said adapter means to effectslowing of said rigid sheet.

2. A mechanism as defined in claim 1 wherein said sheet engaging surfacelies substantially tangential to the outer periphery of said vacuumwheel and substantially parallel to said sheet path when said adaptormeans is in its second position, and wherein said outer periphery ofsaid vacuum wheel engages any rigid sheet which clings on said sheetengaging surface and effects movement of such rigid sheet from saidsheet engaging surface.

3. A mechanism as defined in claim 2 wherein said adaptor meansstraddles said vacuum wheel, and said vacuum wheel periphery rotatesthrough said vacuum chamber.

4. A mechanism as defined in claim 3 wherein said vacuum chamber is atleast in part defined by bottom surface which converges toward saidsheet path as it extends in the direction of sheet movement.

5. A mechanism as defined in claim 1 wherein said means for applying avacuum to said passageways comprises a nonrotatable vacuum shoecommunicating with a source of vacuum and said vacuum passageways insaid vacuum wheel, said means for rotating said vacuum wheel comprises adrive shaft drivingly connected to the vacuum wheel and extendingthrough said vacuum shoe and rotatable relative thereto, and saidadaptor means has a portion encircling said drive shaft and supportedthereby.

6. A mechanism as defined in claim 5 wherein said adaptor meanscomprises a pair of generally annular side members disposed on oppositeaxial sides of said vacuum wheel, and a stop member associated with oneof said side members and said vacuum shoe for preventing rotation ofsaid adapter means.

7. A mechanism as defined in claim 6 further including means forpreventing axial movement of said vacuum wheel and adapter means axiallyrelative to said drive shaft and releasable to permit axial movement ofsaid adapter means and vacuum wheel in one direction relative to saiddrive shaft to a position free of said stop members and at which saidadapter may be rotated be tween its first and second positions and thenmoved axially of said drive shaft in a second direction wherein it againis held from rotation by said stop member.

8. A sheet slow-down mechanism for reducing the rate of speed of amoving sheet after it is released by moving grippers which move thesheet through a path comprising means defining a vacuum chamber which isopen to the atmosphere adjacent the path of sheet travel, said meanshaving a relatively flat sheet engaging surface over which the sheetmoves, means for applying a vacuum to said chamber to draw the sheetagainst said sheet engaging surface to apply a braking force to themoving sheet, and a rotatable Wheel member operatively associated withsaid means and engageable with a sheet on said sheet engaging surface toefiect movement of such sheet from said surface.

9. A sheet slow-down mechanism as defined in claim 8 wherein said sheetengaging surface lies substantially tangential to the outer periphery ofsaid rotatable wheel and substantially parallel to said sheet path andwherein said rotatable wheel comprises a vacuum wheel having vacuumpassageways which open to the atmosphere adjacent the sheet path.

10. A sheet slow-down mechanism as defined in claim 8 wherein said meanshaving a sheet engaging surface comprises an adapter unit movablebetween a first inoperative position and a second operative position andhaving said sheet engaging surface in a position parallel to andadjacent said sheet path when in said operative position.

References Cited UNITED STATES PATENTS 2,657,052 10/ 1953 Elliott 271793,336,028 8/1967 Schonmeier 271-74 RICHARD E. AEGERTER, PrimaryExaminer.

